In situ oxygen isotopic measurements of primary and secondary minerals in Type C CAIs from the Allende CV3 chondrite reveal that the pattern of relative enrichments and depletions of
16O in the primary minerals within each individual CAI are similar to the patterns observed in Types A and B CAIs from the same meteorite. Spinel is consistently the most
16O-rich (Δ
17O = −25‰ to −15‰), followed by Al,Ti-dioside (Δ
17O = −20‰ to −5‰) and anorthite (Δ
17O = −15‰ to 0‰). Melilite is the most
16O-depleted primary mineral (Δ
17O = −5‰ to −3‰). We conclude that the original melting event that formed Type C CAIs occurred in a
16O-rich (Δ
17O
−20‰) nebular gas and they subsequently experienced oxygen isotopic exchange in a
16O-poor reservoir. At least three of these (
ABC,
TS26F1 and
93) experienced remelting at the time and place where chondrules were forming, trapping and partially assimilating
16O-poor chondrule fragments. The observation that the pyroxene is
16O-rich relative to the feldspar, even though the feldspar preceded it in the igneous crystallization sequence, disproves the class of CAI isotopic exchange models in which partial melting of a
16O-rich solid in a
16O-poor gas is followed by slow crystallization in that gas. For the typical (not associated with chondrule materials) Type C CAIs as well for as the Types A and B CAIs, the exchange that produced internal isotopic heterogeneity within each CAI must have occurred largely in the solid state. The secondary phases grossular, monticellite and forsterite commonly have similar oxygen isotopic compositions to the melilite and anorthite they replace, but in one case (CAI
160) grossular is
16O-enriched (Δ
17O = −10‰ to −6‰) relative to melilite (Δ
17O = −5‰ to −3‰), meaning that the melilite and anorthite must have exchanged its oxygen subsequent to secondary alteration. This isotopic exchange in melilite and anorthite likely occurred on the CV parent asteroid, possibly during fluid-assisted thermal metamorphism.