For years it has been customary for players to look for ways to improve their skills during the off-season. Many MLB players have played winter ball in places like Venezuela and the Carribean.
Today, top prospects are invited to participate in the Arizona Fall League.
From the late 1950's through the late 70's, several MLB teams fielded teams in the Florida Winter Instructional League. The league was designed to give young prospects chances to receive additional instruction under the watchful eye of each team. I can find references to the Orioles fielding teams in 1959, 1962-1968, 1970-1973 and 1976-1977. It looks like most of the games were played at Al Lang Field in St.Petersburg.
I have a few programs from 1964, 1967 & 1969
1964 Program with Manager George Bamberger
Players included Jim Palmer, Mark Belanger and Lou Piniella for the O's
Attachment 393744 Attachment 393748
1967 Programs with Manager Vern Hoscheit
Players included Terry Crowley, Al Severinsen, Bill Dillman and Roger Freed
Attachment 393745 Attachment 393750
Attachment 393746 Attachment 393751
1969 Program with Manager Cal Ripken Sr
Players included "Marcus" Wayne Garland, Johnny Oates and Jesse Jefferson
Attachment 393747 Attachment 393752