I am trying to loop through a list of team members on an opportunity and am having troubles. Here's the piece that isn't working how I need it to:

        for (Opportunity opp : tNewMap.values()) {

//This code section works, but obviously really bad for bulk loads

                List<OpportunityTeamMember> oppMembers = [SELECT UserId FROM OpportunityTeamMember WHERE OpportunityId =: opp.Id];      
                for (OpportunityTeamMember otm : oppMembers) {

//This doesn't work and I'm not sure why
                for (OpportunityTeamMember otm : opp.OpportunityTeamMembers) {

Any advice?