In this article, we sought to isolate the processing demands of combining the concepts of modifier-noun phrases from those of other language comprehension processes. Probe reaction time (RT) was used as an indication of the processing resources required for combining concepts. Phrase frequency (as measured by Google hit rates) was used as a metric of the degree of conceptual combination required for each phrase. Participants were asked to interpret modifier-noun phrases using a sense-nonsense decision (Experiment 1) and a phrase meaning access task (Experiment 2). Experiment 2 also used a lexical decision task to activate the word’s individual meanings. Regression analyses for both experiments indicated that phrase frequency (indicating novelty) predicts a significant portion of the probe RT variance, such that low-frequency phrases required more processing resources than high-frequency phrases, when controlling for associative strength, word frequency, letter length, and lexical-semantic activation. Overall, this study indicates that conceptual combination requires processing resources beyond those of other language processes.