Inspired by a post on BeyondTheBoxScore (which was inspired by a post on LoneStarBall) - and with the assistance of the historical Wins Above Replacement developed by Sean Smith (of CHONE fame) - I'm going to do my best to go through the best O's at each position (of the Retrosheet Era - 1955 and later). Yaye!
I'm going to list it as O's career WAR / best season WAR (as an Orioles) / peak WAR (top 5 seasons, non-sequential). (These aren't exclusively for games played at the given position - just years where it was their primary position.)
C: Chris Hoiles - 23.2/7.0/18.8. Hoiles could hit well for a baseball player, and especially for a catcher (+82 runs on with the bat). His defense wasn't as bad as his reputation (a modest +7 runs total for his 10 years), and he had a monster 1993 season (7 WAR, .310/.416/.585, 29 HR, 162 OPS+). I knew it would be Hoiles, and yet I'm still kind of surprised by that.
Runner-up: Rick Dempsey - 20.7/3.3/13.5. The guy couldn't really hit (-43 runs with the bat), but he was a very good defensive catcher (+59 runs) and was with the team for part of 12 seasons.
caught a bunch of games with the team in the early 1900s and swing an OK stick for a catcher (.289/.342/.367, 92 OPS+).
1B: - 54/7.2/30.6. Eddie went from consistently very good (4.5, 4.5, 4.5, 3.9 (missed time) - in his first 4 years at first, after one as the DH) to great (5.6, 7.2, 7.0, 6.3) before going down-hill and and being traded (4.2, 3.8, 2.5). The guy was almost absurdly consistent, posting an OPS+ of 156 four years in a row. He even had a quality glove early in his career (+9 and +10 runs, in his 7.2 and 7.0 WAR seasons of 1983 and 1984).
Runner-up: Boog Powell - 30.5/5.8/22.4. He was still an outfielder, but 1964 was a pretty good year - .290/.399/.606, 39 HR, 176 OPS+ for +45 runs with the bat and only -1 with the glove. At first, 1970 saw more total offense (46 runs; .297/.412/.549, 35 HR, 163 OPS+) but in much more playing-time (635 PA vs. 502 PA in '64).
(25.8/6.4/24.2) wasn't with the team long enough. George Sisler (.340/.379/.468, 124 OPS+) played too long ago to check out.
2B: Bobby Grich - 26.8/7.5/26.8. And that doesn't include his partial season at second in 1972 (5.6 WAR, but only 45 games at second with 81 at short). The guy was a well above-average hitter (+91 runs in just his four years at second) and and good defender (+50 runs). 1973 looks bad (.251/.373/.387, 116 OPS+) but the +29 runs with the glove made it the best season of his career.
Runner-up: - 20.1/5.2/18.6. Given his new four-year contract extension, I think Brian is going to lock this spot down eventually.
Davey Johnson (17.3/4.4/14.8) was close. Funny thing; Johnson's big 43 HR season with the Braves was less valuable than his 18 HR season with the O's (4.2 WAR to 4.4) because his baserunning (-5 to 0) and defense (-10 to 2) both got worse. Roberto Alomar also comes pretty close (13.1 WAR) in just three seasons with the team.
Ski Melillo (.260/.306/.340, 63 OPS+) played the most games at the position as an Oriole, but that was back in the 20s and 30s.
3B: Brooks Robinson - 70.4/8.0/33.6. Brooks put up a lot of great seasons, with his best actually coming in a year where his famed defense (+294 run career) was merely "very good". That was in 1964 (8.0 WAR) when he put up 37 runs of production with the bat (.317/.368/.521, 28 HR) and only 17 with the glove. That 17 is actually only the 9th best season of his career. Spending one' entire career at the same position with the same team probably helps too.
Runner-up: - 20.4/6.5/18.8. DeCinces was only the starter for six years, but he never got more than 588 PA with the team. His best career season actually came the year after he left the Birds, when he got 642 PA with the Angels and put up 7.4 WAR. His 6.5 win season with the O's had 31 runs of offense (.286/.346/.526, 28 HR) and 11 runs of defense - which looks pretty similar to Brooks' best year.
(.272/.390/.441, 116 OPS+ for all teams in his career) and Jimmy Austin (.246/.326/.314, 90 OPS+) may have cases based on longevity (1419 and 1187 games at third respectively), but they're too far back in the past. Melvin Mora (16.8 WAR in his third-base seasons) may have a claim on third place, as well.
SS: Cal Ripken Jr. - 86/10.8/42.2. The Iron Man has the reverse situation of DeCinces, in that he always had well over 600 PA. That 1991 season (10.8 WAR) saw call put up 48 runs with the bat (.323/.374/.566, 34 HR) and 23 with the glove as a short-stop. That is crazy valuable. How good was Cal? If he had had an average bat (0 runs instead of +181 career) he still would have had a higher total WAR than Brooks Robinson (72.9 vs. 70.4). Same thing if he had had an average glove (0 runs instead of +181 career, again - amazing talent on both sides of the ball). Now that is a Hall of Famer.
Runner-up: Mark Belanger - 32.2/5.3/20.8. And it was all glove; 235 runs on defense and -245 runs on offense. His best year was 1976 when he didn't completely suck with the bat (-2 runs, .270/.336/.326) and was his usual stellar self with the glove (+24 runs).
Bobby Wallace (.268/.332/.358, 105 OPS+ for all teams in his career) and Vern Stephens (.286/.355/.460, 119 OPS+) probably wouldn't catch Belanger, but the WARs aren't readily available.
OF: - 33.4/7.1/24.3. That 50 HR, 7.1 WAR season sure helped his cause, though Brady was a pretty good hitter in general (+109 runs total with the O's). I had always assumed that he was a good outfielder too, but it looks like he was only around average (-1 runs total, with a high of +10 and a low of -20). The solid base-running (+21 runs) was handy as well.
OF: - 33.1/8.3/30.5. +75 runs with bat in '66 (.316/.410/.637, 49 HR, 198 OPS+) may be the best season at the plate by an O's player ever. He was above-average with the glove before he joined the team, but regressed to a little below average (-14 runs total, in his 6 years).
OF: Paul Blair - 32.3/6.8/27.2. I find it interesting that despite being with the team for 12 seasons (and 8 games in 1964), almost all of Blair production occured in 5 years. The guy was an OK hitter until the end of his career (+26 runs in his first 10 seasons; -51 runs in his last two with the O's, and -32 after that) - especially in 1967 (+24 runs, .293/.353/.446, 135 OPS+) - but he made his name with his glove (+134 runs, with another +34 for his arm).
Runner-up: Ken Singleton - 29.8/5.8/17.2. He wasn't a good defender (-37 runs, with -26 for his arm) but could sure swing the bat; especially in 1977 (+57 runs, .328/.438/.507, 24 HR, 165 OPS+). He actually matched his 5.8 WAR that year in 1979 as well, though with less offense and less-bad defense.
The problem in the outfield is that only two players - Blair and Baby Doll Jacobson (seriously) have played at least 1000 games at on outfield position for the team. Brady did in total, but that was split between center and left. is at 13 WAR already, so he may actually catch up (or even take the top spot) in just the 6 years he has left on his contract. I know I'm prone to hyperbole with regards to Markakis ($66 M is a steal!), but it's kind of neat that we may be seeing the best outfielder in the history of the team out there now.
So here's you're all-time (since 1955) O's line-up:
C: Chris Hoiles
1B: Eddie Murray
2B: Bobby Grich
3B: Brooks Robinson
SS: Cal Ripken Jr.
LF: Brady Anderson
CF: Paul Blair
RF: Frank Robinson
And the over-all rankings(ish):
#10: Ken Singleton (30.9/5.8/17.2, with his time at DH)
#9: Mark Belanger (32.2/5.3/20.8)
#8: Paul Blair (32.3/6.8/27.2)
#7: Brady Anderson (33.4/7.1/24.3)
#6: Bobby Grich (33.1/7.5/32.4 including his time at short)
#5: Frank Robinson (33.1/8.3/30.5)
#4: Boog Powell (38.1/6.1/25.8, with his time in the outfield)
#3: Eddie Murray (57.1/7.2/30.6, with his time at DH)
#2: Brooks Robinson (70.4/8.0/33.6)
#1: Cal Ripken Jr. (91.2/10.8/42.2, with his time at third)
These are the kinds of lists it's easier to make (for the players) by sticking with a team for a while. I think that #5-9 are grouped closely enough that the rankings are judgment calls. After that it's pretty easy to rank the top four.
Unfortunately, the pitching WAR is not as readily available. That means another method is going to need to be used. I'm going to go with the BaseballProspectus stat PRAR - pitcher-only runs above replacement. It's runs instead of wins, but I don't especially want to do the conversion. (O's career PRAR / best single-season PRAR / top five PRAR.)
SP1: Jim Palmer - 656/73/342. Palmer's 126 ERA+ is 6th all-time for the Birds; his 53 shutouts are easilly first; as are his games started (521), innings (3948), and K's (2212), and wins (268). He's also second in winning percentage (.638). Notice the quality of defense that Palmer pitched in front of.
SP2: - 517/75/298. He's third in team history in ERA+ (129); second K's (1535) and K:BB ration (3.29); sixth in K/9 (6.87) and BB/9 (2.09); fifth in games started (288); seventh in innings (2009.7); third in wins (147) and first in winning percentage (.645). I'm now pretty comfortable saying that - including his Yankee years - Mussina was better than Palmer. Jim is still easilly the best O's pitcher, though.
SP3: Dave McNally - 262/74/212. He's second in shutouts for the O's with 33; second in games started (384), innings (2652.7), and wins (181); seventh in complete games (120); third in K's (1476); and fifth in winning percentage (.612).
SP4: Milt Pappas - 246/46/195. He's fifth in shutouts (26); ninth in games started (232); sixth in K's (944); and seventh in winning percentage (.598).
SP5: Mike Flanagan - 208/37/147. He's tenth in shutouts (17) and complete games (98); third in games started (328) and innings (2317.7); fourth in K's (1297); and fifth in wins (141).
SP6: Mike Cuellar - 175/50/178. He's third in shutouts (30); sixth in games started (283), innings (2028.3), and complete games (133); fifth in K's (1011); fourth in wins (143); and third in winning percentage (.619).
If we include the pre-Retrosheet time, then Urban Shocker (342/65/283) slots into the third spot pretty comfortably. It's nice that the five-year totals and the overall rankings line-up pretty well.
So mixing the pitchers with the position players the top 10 looks more like this:
#10: Paul Blair (327 runs above replacement - 32.3 wins above replacement)
#9: Brady Anderson (345 - 33.4)
#8: Bobby Grich (314 - 33.1)
#7: Frank Robinson (298 - 33.1)
#6: Boog Powell (346 - 38.1)
#5: Mike Mussina (517 - around 50, assuming slightly over 10 runs/win)
#4: Eddie Murray (550 - 57.1)
#3: Jim Palmer (656 - Sean Smith has him at 64.5 WAR, which is close to 10 runs/win)
#2: Brooks Robinson (700 - 70.4)
#1: Cal Ripken Jr. (904 - 91.2)
It's not definitive, but I think it's close. For your viewing pleasure (click for clearer picture):